This is an application for a Research Scholar Development Award (K22) from the NIAID. The applicant, Andrew C. Stubbs, PhD, is currently a post-doctoral fellow at the University of Colorado Health Sciences Center. If successful, this award will help the candidate achieve his aim-to establish an independent research initiative at an academic institute of scientific excellence. It is the intention of the applicant to pursue an academic career plan that will both support his scientific development through the provision of the resources necessary for his continued work towards the development of novel vaccine strategies for induction of cell-mediated immune responses. To this end, this application seeks to investigate the mechanisms behind a series of observations made by the candidate during his post-doctoral training. Specifically, the ability of dendritic cells (DCs) to initiate cell-mediated immune responses after exposure to an antigen (Ag) together with an inflammatory microbial stimuli, may offer the potential for the development of novel adjuvant and antigen formulations for the induction of cell-mediated immunity. DCs are professional antigen presenting cells (APCs) involved in the initiation of both innate and adaptive immune responses. Two major subsets of DCs, myeloid DCs (MDCs) and lymphoid DCs (LDCs), have been shown to play an important role in mediating cellular immune responses. DCs express cell-surface molecular pattern recognition receptors (PRRs) with specificity for pathogen associated molecular patterns (PAMPs). The ligation of PRRS on DCs by PAMPS is likely to profoundly affect the properties of cellular activation, antigen processing, presentation and immunogenicity of activated DCs, and may represent a mechanism by which DCs are able to perceive an immunologic challenge and subsequently orchestrate an appropriate immune response. We and others have recently demonstrated that DCs exposed to certain inflammatory microbial stimuli may initiate cytotoxic T lymphocyte (CTL) responses, which depend on MHC class I restricted processing and presentation of exogenous antigen (Ag), in the absence of T cell help. We hypothesize that certain microbial stimuli activate DCs via PRR ligation, and that such ligation may profoundly affect the subsequent ability of DCs to a) process exogenous Ag via the MHC class I pathway, and b) initiate subsequent CTL responses. The purpose of this proposal is to investigate the mechanisms employed by, and the relative ability of, different DC subsets exposed to an exogenous model antigen, chicken ovalbumin (OVA), in the presence of different TLR ligands, to cross-present exogenous Ag and prime CTL responses, and the dependence of such responses on Th-cooperation. Information gained form the proposed experiments will be useful in designing vaccine strategies for the prophylactic and therapeutic treatment of diseases such as HIV, tuberculosis and cancer. [unreadable] [unreadable]